Garcetti had jumped out to a lead in post-midnight returns and delivered what sounded like a victory speech, then shortly before 3 a.m. tweeted a thank-you to his supporters: "Thank you Los Angeles," he wrote, "The hard work begins but I am honored to lead this city for the next four years. Let's make this a great city again."

The first batch of absentee results had put Greuel slightly ahead, but as the vote counts continued rolling in, each one delivered a stronger margin to Garcetti. Just after 3 a.m. Wednesday morning, with 100 percent of precincts reporting, Garcetti led Greuel with 53.9 percent of the vote to Greuel's 46.1 percent.

Garcetti entered the Hollywood Palladium ballroom around 11:40 p.m. Tuesday as Sam and Dave's "Hold On I'm Coming" blasted through the loudspeakers. After hugging supporters and family members with a broad grin on his face, he thanked Greuel for her service and spelled out his vision to lead the city.

"Tomorrow we roll up our sleeves and we get to work rebuilding a great Los Angeles. Thank you Los Angeles. Onward," he declared.

His family joined him on stage, including wife Amy Wakeland, and his father, former District Attorney Gil Garcetti, as well as the three former mayoral candidates who endorsed him, Councilwoman Jan Perry, talk radio host Kevin James and tech executive Emanuel Pleitez.

Reflecting the diverse make-up of Garcetti supporters, the crowd at the Hollywood Palladium included tech entrepreneurs, Teamsters members, and Peru Village neighborhood residents.

Greuel, however, did not concede the race early on, telling supporters around 11 p.m. on Tuesday that it continued to be tight, and noting that she won her first City Council campaign by just 225 votes.

"So, ever since then, I have run every campaign knowing that every single vote counts," she said.

Whatever the final results, the city's voters would make history, choosing either the first woman or first Jewish elected mayor of Los Angeles. The next mayor would take office at a time when the city continues to face tight finances and a loss of basic city services and workers.

Tuesday's election closed a two-year, $33 million race to succeed outgoing Mayor Antonio Villaraigosa, who is termed out next month.

Garcetti political consultant Bill Carrick said he wasn't surprised that Greuel did well in the first results, which reflected absentee votes cast by mail. Greuel had spent her funds early in the race in an effort to target absentee voters who were mailing in ballots weeks ahead of the election, a tactic which left her short on cash for TV spending toward the end of the campaign and gave Garcetti a bigger airwave advantage leading up to election day.

"We anticipated she would do well with early absentee voters," Carrick said, speaking Tuesday night at the Garcetti campaign's party at the Palladium.

"The LMU poll shows that we are doing substantially better than her at the polls."

Loyola Marymount University conducted exit polling of 800 voters which projected Garcetti would win by a 54-46 margin.

Students at the school's Thomas and Dorothy Leavey Center for the Study of Los Angeles spoke in English and Spanish to voters at 25 precincts and talked by telephone to those who had cast absentee ballots. The survey has a margin of error of plus/minus 3.46 percent.

Center director Fernando Guerra said he was surprised at some of the results: While Greuel did well in the school's survey among African-American voters, capturing 71 percent of those votes, she managed only an equal split with Garcetti among women voters.

"The thinking was she needed to do better among women to stand a chance," Guerra said.

Garcetti also carried white voters, Guerra said.

In the San Fernando Valley, Greuel was favored by only a 50.5-49.5 margin, far below what she needed in order to win, Guerra said.

Former Assembly Speaker Bob Hertzberg, a co-chair of the Greuel campaign, said it is likely that 40,000 to 50,000 ballots would not be counted by the end of election night, but the candidate's early lead was heartening to supporters. He also said about half the ballots would be cast absentee.

The race featured two liberal City Hall Democrats. Greuel emphasized the historic nature of her bid to be the city's first female mayor, while Garcetti highlighted his multi-cultural roots, saying his mixed Italian, Mexican and Jewish heritage reflected the diversity of Los Angeles.

But beyond those distinctions, their similarities on policy made it harder for voters to define the differences between them, forcing the candidates to be more aggressive over issues such campaign fundraising and union support.

Raphael Sonenshein, executive director of the Pat Brown Institute of Public Policy at Cal State Los Angeles, said there were no big issues on the ballot to draw voters to the polls.

"Neither one of these candidates have the depth of a base of support to draw on," Sonenshein said. "If you go back over the last five elections, you were looking at candidates with a substantial base that would go with a candidate. You don't see that in this race.

"Both are solid, moderate to liberal Democrats and a lot of people like them both and don't see many differences. As a result, they see no strong reason to vote."

Steve Braun, 36, of Studio City said he chose Greuel because he believes she may be more likely to listen on immigration issues. A Canadian native, Braun said he had recently become an American citizen.

Tony Hey of Studio City was the first to vote in his precinct on Tuesday. He said he found the two candidates acted "equally repulsive" during the debates, but he chose Garcetti because of a Salma Hayek commercial in which the actress spoke highly of the 42-year-old councilman.

"She made him seem so nice and honest," Hey said. "In terms of voting, I see it like charity. It's a responsibility."

Voter Debra Graff said she found it difficult to choose between the two candidates, and said she just wanted the new mayor to be a good person.

"I just want him or her to be kind and help people who need help," Graff said. "I already love L.A. It's a great city. And both candidates seem so dedicated."

With the city's budget a focal point in the election, Greuel repeatedly blamed Garcetti and the rest of the council for failing to rein in waste and spending. In turn, Garcetti questioned Greuel's claim of finding $160 million in savings, and accused her of sitting on the sidelines during tough budget cuts.

With deep ties in the political and entertainment fields, Greuel and Garcetti were able to raise millions of dollars for their campaigns.

Greuel, a former City Councilwoman representing the east San Fernando Valley who won the controller's seat in 2009, garnered $7 million during the race. Garcetti, who has represented the Hollywood area since 2001 and was twice elected as council president, raised $8 million.

Greuel also benefited from an outside spending million advantage over her opponent. Outside groups, or super PACs, spent more than $7.5 million on her behalf, with the most support coming from unions at the Department of Water and Power, which helped raise more than $4 million for Greuel.

By contrast, Garcetti received $2.2 million in support from super PACs.

But in a low turnout election, the campaign's negativity may have turned off voters.

Only 21 percent of voters cast ballots in the March primary, continuing a trend of low civic engagement in Los Angeles mayoral elections. In the 2005 race between Villaraigosa and incumbent James Hahn, 28 percent of registered voters cast ballots.

Absentee voters accounted for roughly half of all votes cast in the primary, and those votes are being closely watched in the run-off.

By Tuesday night, 174,457 vote by mail ballots -- out of 739,147 ballots sent out -- had been returned, a 23.6 percent return rate.